Incorporation of cortical bone autografts following intraoperative extracorporeal irradiation in rabbits.

In an experimental study using 60 rabbits, a cortical bone segment of the unilateral tibial diaphysis was resected, irradiated extracorporeally, and reimplanted immediately as an autograft. The subsequent process of graft incorporation was examined over a 26-week period by roentgenography, histology, and histomorphometry. The irradiation doses were 0 (control), 50, 100, and 200 Gy. Roentgenographic and histologic examinations revealed that cortical bone autografts irradiated at 50 to 200 Gy were incorporated in the same manner as non-irradiated controls. By histomorphometry, the mean unresorbed fraction of the grafts at 6 weeks post-implantation was estimated to be 88.4% for the control group and 89.4% for the 200 Gy group. That of 26 weeks postimplantation was 17.5% for the control and 28.5%, 26.1%, and 27.8% for the 50, 100, and 200 Gy groups, respectively. Cumulative new bone formation showed a similar but inverse pattern of difference between the control and irradiated groups at 26 weeks. However, these differences were not statistically significant and were considered to be slight when compared with the overall similarity of the process. The total cross-sectional area of cortical bone at 26 weeks was similar to that of the contralateral side in all groups. In none of the adopted evaluation methods was any difference detected among the three irradiated groups with different doses. The results of this study suggest that extracorporeal irradiation of autografts at the specified doses impairs possible cellular contribution of the grafted marrow to the incorporation process, but does not interfere with the contribution of the matrices. The results provide useful information concerning the method of limb salvage surgery using intraoperatively-irradiated autografts.